Aerosol Climatology over the Bay of Bengal and Arabian Sea Inferred from Space-Borne Radiometers and Lidar Observations

Abstract

Atmospheric aerosols over the oceanic region are very important air pollutant and play a vital role in Earth's radiation budget and climate change. This study presents the aerosol climatology over the Bay of Bengal (BoB) and Arabian sea (AS) using long term (2006)(2007)(2008)(2009)(2010)(2011)(2012) data from space-borne radiometers [Moderate-Resolution Imaging Spectroradiometer (MODIS), Ozone Monitoring Instrument (OMI)] and space-based active lidar onboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO). AS experiences higher AOD as compared to that over BoB during the study period. A good periodicity along with strong intra-seasonal/annual variability in aerosol loading is also observed over both the study regions. Approximately one month lag is found for maximum aerosol loading period over AS and BoB for almost every year i.e., June-July for AS and May-June for BoB. This lag could be explained by pathway and timing of summer monsoon over the Indian subcontinent. Elevated layers of absorbing dust up to 2-4 km altitudes are observed during the pre-monsoon and monsoon seasons over both the regions. The CALIPSO measurements show strong seasonal heterogeneity in aerosol properties over both the regions, which is well corroborated with MODIS and OMI observations. This significant seasonal heterogeneity in aerosol loading has been explained by the role of transportation of aerosols from various emission sources using NOAA HYSPLIT back trajectory model at three different altitude levels viz. 500, 1500 and 2500 m height. The possible role of Indian summer monsoon in modulating the aerosol behaviour over AS and BoB is another important aspect of this study that need further analyses using higher spatio-temporal resolution data.

Improved air quality during COVID-19 at an urban megacity over the Indo-Gangetic Basin: From stringent to relaxed lockdown phases

“…Result could be associated with the reduction in the emission sources across the IGB due to the current pandemic situation. It is to be noted here that the enhanced aerosol loading over the IGB is usually the main cause of increase loading over the BoB through IGB-outflow ( Srinivas et al, 2011 ; Tiwari et al, 2016 ; Singh et al, 2020 ). Furthermore, the IGB is situated in the vicinity of the Desert regions, and thus largely impacted by the frequent occurrence of dust aerosols during March-June ( Pandithurai et al, 2008 ; Srivastava et al, 2014 ; Dumka et al, 2019 ) even though negative change in aerosol loading indicate that anthropogenic aerosol emission override the natural local or transported aerosols.…”

Aerosol Induced Changes in Sea Surface Temperature Over the Bay of Bengal Due to COVID-19 Lockdown

“…The Indian Ocean rim countries (especially in South Asia) have undergone significant economic growth in recent times with increased emissions and thus atmospheric aerosol loading (Moorthy et al, 2013). The continental outflow, especially from the heavily aerosol laden Indo-Gangetic Plains (IGP), dominates the aerosol loading over the BoB region (Satheesh et al, 2001(Satheesh et al, , 2006Vinoj et al, 2004Vinoj et al, , 2010Moorthy et al, 2009;Nair et al, 2014;Tiwari et al, 2016) during pre-monsoon (March to May) and the winter (December to February) season. Thus BoB is heavily affected by fine anthropogenic particulates as indicated by the high Angstrom Exponent (AE) (see Figure 1) compared to the Arabian Sea (Vinoj and Satheesh, 2003).…”

Near‐Future Anthropogenic Aerosol Emission Scenarios and Their Direct Radiative Effects on the Present‐Day Characteristics of the Indian Summer Monsoon

“…Also, the dust source emission scheme is very sensitive to the soil parameters, which can strongly influence model biases. In addition, the model underestimates the total AOD over parts of the central to eastern IGB and over the northern Bay of Bengal, where the outflow of aerosols from the Indian continent occurs due to the prevailing wind circulations (Tiwari et al, ). On the other hand, the IGB also consists of some anthropogenic aerosol species that are not considered in the model, such as secondary OC aerosols, inorganic aerosols, and brown carbon (Chakraborty et al, ).…”